What might cause pain in the kneecap when bending the knee?

When you bend your knee, the kneecap (patella) slides over the thigh bone. Sometimes the surfaces do not move smoothly, and this can irritate the soft tissues between them. This irritation is known as patellofemoral pain syndrome. It is common in people who are active or who do sports that involve a lot of running, jumping, or bending, which is why it is often called runner's knee. Overusing your knee or improper technique during activities may lead to this pain. Additionally, if the kneecap is not aligned properly, it can put extra pressure on certain areas of the knee. This extra pressure can cause soreness or pain when bending, especially during activities like climbing stairs or squatting. Sometimes, the tendon that connects the kneecap to the shinbone can become inflamed, also causing pain. It is important to rest, use ice, and try gentle stretching or strengthening exercises to help the knee heal. Less commonly, knee pain accompanied by other symptoms like fever, swelling and redness may be a sign of an infection. If the pain continues, you can use Ubie's free AI symptom checker to better understand what might be causing your discomfort and determine whether you should seek medical attention.